This invention relates to a variable speed motor for a compressor that is incorporated into a refrigerant system with a reheat function.
Refrigerant systems are utilized in many applications such as to condition an environment. Air conditioners and heat pumps are used to cool and/or heat the air entering an environment. The cooling or heating load on the environment may change with ambient conditions, and as the temperature and/or humidity levels demanded by an occupant of the building vary. Obviously, the refrigerant system operation and control have to adequately reflect these changes to maintain stable temperature and humidity conditions within the environment.
In some cases, while the system is operating in a cooling mode, the temperature level of the indoor air stream to provide a comfortable environment in a conditioned space may need to be higher than the temperature that would provide the ideal humidity level. On the other hand, lower the temperature of the air stream, more moisture can be removed from the air. These contradicting trends presented challenges to refrigerant system designers. One way to address such challenges is to utilize various schematics incorporating reheat coils. In many cases, a reheat coil placed on the indoor air path downstream of the evaporator is employed for the purposes of reheating the air supplied to the conditioned space, after it has been cooled in the evaporator, and where the moisture has been removed.
In the prior art, controls can be programmed to optionally actuate the reheat function. However, the humidity control provided by the reheat circuit is increased or decreased in steps. It would be desirable to provide the ability to vary the humidity control between these discrete steps.
In the past, attempts have been made to apply modulation or pulsation techniques to split and regulate refrigerant flow between a main circuit and a reheat branch. These approaches have not been found to be robust, and have strict limitations regarding their application range.
Variable speed drives are known for driving compressors at a variable speed in a refrigerant system. By driving the compressor at a higher or lower speed, the amount of refrigerant that is compressed changes, and thus effecting operational characteristics and system capacity.
Generally speaking, variable speed drives have not been utilized in refrigerant systems incorporating a reheat function for continuous dehumidification capability adjustment, and specifically in the refrigerant systems with variable sensible heat ratios. Thus, refrigerant systems that have incorporated a reheat function have been limited, in general, to providing the humidity control in discrete steps or over a narrow range of operating parameters.